The invention pertains generally to substituted aromatic nitrile synthesis and particularly to the specific substitution of the phthalonitrile ring with an iodo-group or a fluoroalkyl group.
Polyphthalocyanines have become an important structural material, possessing many properties superior to polyimides and epoxies. Presently, these compounds are prepared by polymerizing bisorthodinitriles, which are structurally two phthalonitriles connected by a bridging group. It is the bridging group that determines, to a major degree, the properties of the resulting polymer. Many excellent possible bridging groups are fluorinated which makes the synthesis of bisorthodinitriles with these groups unlikely by existing methods, such as a nucleophilic displacement of the nitro group of nitrophthalonitrile. An iodocoupling reaction may provide a synthesis for fluorocarbonbridged bisorthodinitriles, but the necessary iodo-compounds have not been prepared.
Several problems exist with the synthesis of these iodo-compounds. Due to the strong electron acceptance of iodine, this halogen, unlike bromine or chlorine, forms complexes with aromatic compounds when reacted directly with them. A substituted aromatic ring, such as the phthalocyanine ring, is difficult to substitute at a specific position with a fluorocarbon group due to the fluorocarbon being a very weak nucleophile.
A specific fluoroalkyl substitution on the phthalonitrile ring has importance besides the synthesis of fluorocarbon-bridged polyphthalocyanines. The specific substitution allows greater control of the properties and costs of fluorocarbon-substituted phthalocyanines which are formed from phthalonitriles.